The present invention relates to an electrohydraulic control system for a backup hydraulic power steering system and more particularly relates to improvements in the control system disclosed in U.S. Pat. No. 3,820,620 issued to Miller et al. on June 28, 1974.
The patented control system includes electrical circuitry for automatically checking out the electrical power circuit of the backup system and for arming the circuit for subsequent automatic energization of the backup system upon failure of the main power steering system, during each starting cycle of the vehicle ignition switch means. Operability of the power circuit is indicated by a flashing light or some other warning device and a light becomes lit whenever the system is properly armed.
The patented control system has the following drawbacks:
1. The circuitry does not provide any means for apprising the operator of a failure of the backup steering system to supply adequate steering fluid. PA1 2. The arming indicator light is always lit when the arming circuit is energized and may become subconsciously ignored by the operator. PA1 3. The arming circuit may become inadvertently disarmed by an operator who turns the ignition switch "off" then back "on" again before the flywheel action of the engine ceases thus resulting in the engine continuing to run for operating the vehicle without the backup steering system being readied for automatic operation in the event of failure of the main steering system.